Date: Tue, 7 Feb 2012 13:40:01 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org, davidxu@freebsd.org Subject: Re: [ptrace] please review follow fork/exec changes Message-ID: <201202071340.01126.jhb@freebsd.org> In-Reply-To: <4F30968B.5060101@gmail.com> References: <749E238A-A85F-4264-9DEB-BCE1BBD21C9D@juniper.net> <4F2094B4.70707@juniper.net> <4F30968B.5060101@gmail.com>
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On Monday, February 06, 2012 10:12:11 pm David Xu wrote: > On 2012/1/26 7:48, Dmitry Mikulin wrote: > > <snip> > > > The debugger needs to intercept fork() in both parent and child so it > > can detach from the old process and attach to the new one. Maybe it'll > > make more sense in the context of gdb changes. Should I send them too? > > Don't think Marcel included that patch... > > > >> > >> Does the orphan list change intended to not lost the child after fork ? > >> But the child shall be traced, so debugger would get the SIGTRAP on > >> the attach on fork returning to usermode. I remember that I explicitely > >> tested this when adding followfork changes. > > > > Yes, the debugger gets SIGTRAPs. The problem arises when the real > > parent of the forked process has the code to collect termination > > status. Since attaching to a process changes the parent/child > > relationships, we need to keep track of the children lost due to > > re-parenting so we can properly attribute their exit status to the > > "real" parent. > > > I recall that someone brought a topic in the list said that this should > be fixed, debugging a process should not change > parent-child relation, instead a new link list data structure should be > added to struct proc to trace debugged process, > this will make code clean with a small memory overhead. Yes, I have some old patches to start on this, but I hadn't really finished them, and it makes wait() a bit more complicated. It would be nice if ptrace() had its own pwait() or some such instead of overloading wait(). -- John Baldwin
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